Factors Affecting Dehydrogenation and Catalytic Activity: Methyl Substituent

Autor: Wang Hai, Renwei Xu, Yu Tang, Peng Zhang, Panpan Zhou
Rok vydání: 2018
Předmět:
Zdroj: Catalysis Letters. 148:2683-2695
ISSN: 1572-879X
1011-372X
DOI: 10.1007/s10562-018-2461-x
Popis: Metallocene compound is supported on methylaluminoxane (MAO) and the carrier to form the metallocene catalyst, where (n-BuCp)2ZrCl2 and (1,3-Me,n-BuCp)2ZrCl2 are two typical representatives of the metallocene compounds. The difference in the performances of the two compounds (n-BuCp)2ZrCl2 and (1,3-Me,n-BuCp)2ZrCl2 was calculated by DFT. The introduction of methyl groups led to an increase in the number of Mulliken charge and a decrease in the dipole distance. The results fully confirmed that the methyl group showed an electron-donating effect. The catalyst formed by the metallocene compound (n-BuCp)2ZrCl2 in the olefin polymerization process followed the a-agostic mechanism of ground state and transition state, and dehydrogenation occurred during the polymerization process. In contrast, the catalyst formed by the metallocene compound (1,3-Me,n-BuCp)2ZrCl2 in the olefin polymerization process was based on the Green–Rooney mechanism (hydrogen anion migration), and metal–hydrogen bond and small molecule alkane were formed during the polymerization reaction. However, there were some differences in the mechanism of the homopolymerization and copolymerization when using metallocene catalysts for ethylene polymerization. Ethylene/1-alkene reacted to produce copolymers containing unsaturated bonds, and the results were confirmed by FT-IR analysis. The significant effect of the ligand structure on the metallocene catalyst is beyond imagination, which will lead us to find a suitable ligand structure to meet the high catalytic activity and low hydrogen evolution.
Databáze: OpenAIRE
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